Present hydraulic exercise absorption/control systems for exercise stair devices were devised to offer improved features over older mechanical systems. The most notable of these are Olson et al, U.S. Pat. No. 3,529,474; and Crum et al, U.S. Pat. No. 3,758,112. Neither of these systems provide hydraulic stroke length and adjustment of hydraulically-phased pistons connected to exercise steps. Stroke as used herein refers to the length of travel of the steps in the exercise stair device and, likewise, to the extension of the piston rod attached to the associated step.
Adjustment of stroke length is a very necessary comfort/effectiveness feature in many aerobic and isokinetic exercise activities. Further, for hydraulic exercise absorption and dissipation control systems employing pistons where some leakage of fluid around the piston seals is inevitable, provision for re-establishing stroke is mandatory if the device is to have an acceptable life in relation to use.
Present hydraulic exercise absorption and dissipation control systems phase the pistons either mechanically or hydraulically. Regardless of how the pistons are phased, the stroke length is adjusted (if at all) only by movement of mechanical components such as stops or lever arms.
Quick, convenient adjustment of stroke length is a very desirable feature for any particular user of most exercise equipment. It becomes a comfort/effectiveness necessity when the equipment is used by many people ranging from large to small and fit to infirm. Further, it is mandatory that the usable maximum stroke of the machine not degrade with use over the life of the machine, as can readily happen in piston-based hydraulic systems that do not provide for return of fluid lost past piston seals and for the adjustment of stroke.